In most electronic systems, the desire for smaller devices and the reduced space requirements for installing the smaller devices have resulted in an increased need for efficient electromagnetic interference (EMI) containment. Specifically, due to the proximity of the electronics operating within a system and between two or more systems, electromagnetic interference must be contained to ensure that the operation of one device within one system does not deleteriously effect the operation of another device within the same system or an adjacent system.
For example, in a conventional computer chassis/card cage assembly, multiple slots are available to receive corresponding printed circuit assemblies (PCAs). In most cases, each region/slot in the chassis has either a printed circuit assembly (PCA) disposed therein or a filler panel to enclose or seal off regions/slots of the computer chassis which do not have a PCA. Typically, each region/slot utilizes an electromagnetic gasket (e.g., shield) around the bulkhead of the PCA or the filler panel to ensure EMI containment within the system.
In most cases, the utilization of the PCA, filler panel, chassis, and/or any other devices associated therewith are often defined by an industry standard. Typical standards include, for example, the compact peripheral component interconnect (CPCI) standard, and the VersaModular Eurocard (VME) standard. For example, the CPCI standard dictates that the gap between adjacent units (e.g. adjacent filler panels, adjacent PCAs, or a PCA and an adjacent filler panel) be nominally set at 0.30 millimeters. Thus, when multiple adjacent units are used, the stack-up of tolerances may cause some units to be more than 0.30 millimeters apart, while others may be less than 0.30 millimeters apart. Unfortunately, the size and shape of the electromagnetic gasket utilized therewith are based on the same manufacturing tolerances. That is, each electromagnetic gasket has an amount of manufactured spring and compression corresponding to a gap of 0.30 millimeters. However, because just as described it is not uncommon for adjacent units to have a smaller gap, a significant amount of force may be needed to compress the electromagnetic gasket between the two units. In the alternative case, adjacent units may be far enough apart that the electromagnetic gasket may not have enough spring to maintain adequate EMI containment.
In some cases, this mispositioning with respect to the electromagnetic gasket not only results in a loss or degradation of EMI containment, it may also deleteriously prevent or hinder insertion of a PCA or a filler panel. As explained above, adjacent units may actually end up further than 0.30 millimeters apart from each other. As a result, a unit adjacent to these units may have to be placed in a slot that ends up being less than 0.30 millimeters wide. This may make it difficult to insert the latter unit, in particular with the gasket in its correct position.
At present, one approach to fix the problem described above, is to first have all of the necessary panels (or PCAs) loosely connected to the computer chassis. Once all of the panels are in place, the panels are then carefully tightened to the computer chassis in order to insure that EMI seals are maintained. However, such a method is time-consuming, cumbersome, and lacks a desired “Design for Manufacturability (DFM).”
This problem is particularly egregious in light of the increased prevalence of “hot swapping.” Hot swapping refers to a process in which a PCA is added to or removed from the computer chassis without powering down the system. With hot swapping, it is imperative that any interference is reduced in order to facilitate rapid and perhaps frequent removal and insertion of PCAs and filler panels.
A further problem has arisen with regard to the removal of filler panel assemblies. Specifically, as stated above, a filler panel mounted to a chassis is a tight fit. In fact, the EMI gasket causes a friction force which helps hold a filler panel in-place. Further, the face of the filler panel may be smooth with nothing to grasp. Thus, with a multiplicity of filler panels or complete assemblies mounted on a chassis, removal of a single filler panel may be both difficult and time consuming.